The proposed research is designed to make a fundamental contribution to theories of children's accident prevention in the home. There is an urgent need for developmental accounts of the physical and social systems related to children's home safety and how they relate to one another. The concept of a "safety management system" (SMS) is used here to describe the entire set of factors existing at any one time within a family which help maintain the child's safety in the home. The research is designed to yield a detailed description of the functioning of the SMS within a heterogeneous sample of 27 families over one year. This will reveal the range of types of accident prevention strategies used by parents, and when and how effectively they are combined and actually used. The target children of these families will be girls and boys aged one, two and three. Home visits will be made at 8 week intervals. Interviews and tours of the home with the parent will be the primary methods. Through the comprehensive use of video and audio-recordings, the following types of information will be collected: the changing physical properties of the home in relation to safety, child-related hazards, parent's perceptions of hazards, zones and rules of supervision; accounts of accidents, "near misses" and violations of rules; the child's physical competency and the parent's perception of this; and parent's projections of their child's future competencies and related safety problems. The primary means of recording, comparing and synthesizing data will be mapping. The patterns of interest to this research will emerge primarily from the comparison of mapped data within the family and in the transformation of the family's SMS over time. Comparisons will also be made across families to suggest some of the ways that the SMS's of families differ according to the age and sex of the target child, and of particular characteristics of the family. The research will result in a model of families as safety management systems. This will contribute to the existing accident prevention literature by: helping investigators to interpret the large amount of contradictory findings from their large-scale correlational studies and by developing new hypotheses concerning children's home accidents which can be tested through field experiments. It will also enable the investigators to design and test a home safety diagnostic instrument for parents.